Urgot ultimate doesn't reactivate itself ?

Hello everyone,

His ultimate is supposed to reactivate itself at the end of the 4 seconds if the target is lower than 25%. First of all... Does shield count as health ?

Also... it seems it doesn't work everytime : a friend complained after his first game, my boyfriend can't stop complaining because "he had like 60 hp, and isn't dead, just because I was cc and couldn't press R again myself.."

Someone else got this bug ?